gainward gtx 460 fan too fast

hello
I just bought this gpu (1 gig memory) which constantly has its fan running at 40 % speed, even when its temp is 34 ° c.
I tried the gainward Powertool, the fan section gives only 40 % on manual and sticks to 40% on auto.
I want to lower the fan speed to 35 % minimum and 40 % maximum, how can I achieve this ?
GPU drivers are forceware 260.89, windows 7 64 bits
Thks in advance